EXTRAORDINARY CASE REPORT
Uncommon Tumor, Uncommon Location: A Dermal-Based Spindle Cell/Pleomorphic Lipoma Mark Lincoln, MD and Michael Royer, MD
Abstract: Spindle cell/pleomorphic lipoma is an uncommonly encountered benign neoplasm that is usually found in the subcutaneous tissues. Rare cases reported in the literature have an intradermal location. This lesion usually presents as a subcutaneous nodule on the neck, shoulders, or back of middle-aged to elderly males. Although spindle cell and pleomorphic lipoma are currently considered the same entity, they were historically categorized separately. The authors report a case of hyperpigmented papule with an associated subcutaneous nodule on the left cheek of a 56year-old man, review the literature, and discuss several important diagnostic pitfalls of spindle cell/pleomorphic lipoma. Key Words: skin, neoplasm, benign (Am J Dermatopathol 2016;0:1–3)
INTRODUCTION Spindle cell/pleomorphic lipoma is an uncommon benign soft tissue neoplasm that can rarely occur in the dermis. This unusual presentation can create diagnostic difficulty as the neoplasm is easily confused with other spindle cell processes due to its morphology or with a malignant neoplasm due to its lack of circumscription. Previous terminology of spindle cell/pleomorphic lipomas can also be confusing, as it was originally considered 2 separate entities. We report a case, review the literature, and address the diagnostic challenges of this entity.
adipocytic and spindle cells. The lesion is negative for melan-A, which helps exclude a melanocytic lesion. S100 protein immunohistochemical stain is also negative in the spindle and floret cells, though it highlights the adipocytes. The Ki-67 proliferative index is extremely low (less than 1%). The histologic findings are typical of spindle cell/pleomorphic lipoma (Figs. 3,4).
DISCUSSION Spindle cell/pleomorphic lipoma is a rare, benign adipose tumor. Historically, pleomorphic lipoma and spindle cell lipoma were believed to be separate entities. Further studies demonstrated overlap of their clinical, histologic, and cytogenetic findings.1 They are now considered to be variants of the same entity. The tumor classically presents in the subcutaneous tissues of the shoulders, back, and neck of middle-aged to elderly males as a subcutaneous nodule. Most of these lesions occur in subcutaneous tissues, with a purely intradermal lesion being an unusual presentation.2 Intradermal spindle cell/pleomorphic lipoma has a slight female predominance, as opposed to the male predominance seen in subcutaneous lesions.2,3 Furthermore, intradermal spindle cell/pleomorphic lipomas are most often found on the face.1,3 This is a notably different location compared with the subcutaneous lesion. Clinically, intradermal spindle cell/pleomorphic lipomas are most often diagnosed as a lipoma or a cyst.1 Histopathologically, intradermal and
Case Presentation
A 56-year-old man presented with a slightly raised 8 · 8 mm hyperpigmented, smooth papule on the left cheek with an underlying, freely movable soft subcutaneous nodule. The lesion was present for approximately 2 years. The clinical differential diagnosis included a pigmented nevus. Microscopic examination reveals a nonencapsulated, somewhat ill-defined lesion in the reticular dermis that contains both adipocytes and spindle cells (Fig. 1). The lesion contains a number of large, hyperchromatic “floret-type” cells. Lipoblasts are not seen, and neither mitoses nor necrosis is appreciated (Fig. 2). Immunohistochemical staining shows strong positivity of the floret-type cells for CD34 in both the
From the Department of Pathology, Walter Reed National Military Medical Center, Bethesda, MD. The authors declare no conflicts of interest. Reprints: Mark Lincoln, MD, Department of Pathology, Walter Reed National Military Medical Center. 8901 Wisconsin Ave Bethesda, MD 20889 (e-mail: [email protected]). Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
Am J Dermatopathol Volume 0, Number 0, Month 2016
FIGURE 1. (H&E, ·40) A low power view demonstrates a somewhat ill-defined lesion located in the dermis, consisting of adipocytes and spindle cells. www.amjdermatopathology.com |
Copyright 2016 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
1
Lincoln and Royer
Am J Dermatopathol Volume 0, Number 0, Month 2016
FIGURE 2. (H&E, ·400) A high power view of the spindle cell/ pleomorphic lipoma shows that many of the spindle cells demonstrate striking pleomorphism.
FIGURE 4. (H&E, ·40) A low power view demonstrates a somewhat ill-defined lesion located in the dermis, consisting of adipocytes and spindle cells.
subcutaneous spindle cell/pleomorphic lipomas share many similar features. They are characterized by a proliferation of adipocytes permeated by disorganized spindle cells. The predominant cell type is variable. Large hyperchromatic cells, the floret-type cell, may be observed. Lipoblasts have been reported in some cases.3 Importantly, subcutaneous tumors tend to be well circumscribed, whereas intradermal tumors are usually more infiltrative.4,5 Both intradermal and subcutaneous variants of spindle cell/pleomorphic lipomas may have a myxoid background. A “low fat” or “fat free” variant is reported in the literature that retains all the features of spindle cell/pleomorphic lipomas but has inconspicuous or no adipocytes.6 Overall, these lesions generally have a good prognosis, with excision typically being curative. Some authors have estimated the risk of recurrence to be low, around 1%–2%.3
FIGURE 3. (CD34 immunohistochemical stain, ·200) uniformly strong expression of CD34 is seen in the spindle cells, which permeate throughout the surrounding adipocytes.
Intradermal spindle cell/pleomorphic lipoma presents several pitfalls to the dermatopathologist. Their infiltrative nature raises the possibility of a malignant entity, such as a well-differentiated liposarcoma. Additionally, the presence of lipoblasts may also suggest malignancy. The presence of ropey collagen and loss of Rb protein on immunohistochemistry support the diagnosis of spindle cell/pleomorphic lipoma.7 The RB1 gene is located on chromosome 13q. Deletion of chromosome 13q is characteristic of spindle cell/pleomorphic lipoma, along with loss of chromosome 16q.2 Deletion of chromosome 13q is seen in several other tumors, including mammary-type myofibroblastoma and cellular angiofibroma; loss of nuclear expression for the Rb protein by immunohistochemical stain is an excellent marker for all of these entities.7 Rb protein is also useful in other diagnostic scenarios. For example, cutaneous neuroendocrine carcinoma usually has positive expression, whereas combined squamous-cell carcinoma and neuroendocrine carcinoma have absent Rb expression.8 The rarity of intradermal spindle cell/pleomorphic lipoma makes this entity easy to overlook when considering the histologic differential diagnosis. Prominent myxoid stroma in a spindle cell proliferation may raise the possibility of schwannoma or neurofibroma. The spindle cells in spindle cell/pleomorphic lipoma tend to be stubby, as opposed to the wavy and pointed fibers seen in schwannoma and neurofibroma. Additionally, S-100 protein immunohistochemistry is positive in these 2 entities; whereas it highlights the adipocytes of spindle cell/pleomorphic lipoma; it is negative in spindle cell and floret cells.2,4 Superficial angiomyxoma and myxofibrosarcoma also contain spindle cells in a myxoid stroma and could be considered in the differential diagnosis. Thin-walled, curved blood vessels and neutrophilic infiltrate are characteristic of superficial angiomyxoma and not intradermal spindle cell/pleomorphic lipoma. Myxofibrosarcomas often have thick-walled, curved vessels with adherent tumor cells and tumor cells that resemble myofibroblasts. Intradermal spindle cell/pleomorphic lipomas lack thick-walled
2
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| www.amjdermatopathology.com
Copyright 2016 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Am J Dermatopathol Volume 0, Number 0, Month 2016
vessels and usually do not have stellate cells that resemble myofibroblasts.4 CD34 is a helpful marker to rule in spindle cell/ pleomorphic lipoma because the expression is seen in virtually all cases.7 CD34 can be helpful in differentiating spindle cell/pleomorphic lipoma from other entities, but caution is recommended because CD34 can have some degree of positivity in many of the entities in the differential diagnosis. For example, CD34 expression is seen in schwannoma and neurofibroma.2,4 The expression is usually scattered and seen in small spindle cells in these entities, as opposed to the uniformly strong expression seen in spindle cell/pleomorphic lipoma. A “fingerprint” pattern in CD34 is expressed in many neurofibromas, which is useful to differentiate neurofibroma from desmoplastic melanoma, both of which would be highlighted with S100 protein.9 Myxoid dermatofibrosarcoma protuberans also has strong CD34 expression and could be confused with spindle cell/pleomorphic lipoma. Intradermal spindle cell/pleomorphic lipoma is a rare, but benign, lesion that can easily be confused for a more aggressive lesion. We report a case of an intradermal spindle cell/pleomorphic lipoma on the cheek of a 56-year-old male and review the differential diagnosis, immunohistochemical staining pattern, and common diagnostic pitfalls.
Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
Dermal-Based Spindle Cell/Pleomorphic Lipoma
REFERENCES 1. Rubin BP, Fletcher CD. The cytogenetics of lipomatous tumors. Histopathology. 1997;30:507–511. 2. Cheah AL, Billings SD, Goldblum JR, et al. Spindle cell/pleomorphic lipomas of the face: an under-recognized diagnosis. Histopathology. 2015;66:430–437. 3. French CA, Mentzel T, Kutzner H, et al. Intradermal spindle Cell/Pleomorphic lipoma—a distinct subset. Am J Surg Pathol. 2000;22:496–502. 4. Hornick JL, Brooks JS. Soft Tissues. In: Mills SE, Greenson JK, Hornick JL, eds. Sternberg’s Diagnostic Surgical Pathology. Philadelphia, PA: Wolters Kluwer Health; 2015:148–227. 5. Reis-Filho JS, Milanezi F, Soares MF, et al. Intradermal spindle cell/ pleomorphic lipoma of the vulva: case report and review of the literature. J Cutan Pathol. 2001;29:59–62. 6. Billings SD, Folpe AL. Diagnostically challenging spindle cell lipomas: a report of 34 “low-fat” and “fat-free” variants. Am J Dermatopathol. 2007;29:437–442. 7. Chen BJ, Mariño-Enríquez A, Fletcher CD, et al. Loss of retinoblastoma protein expression in spindle cell/pleomorphic lipomas and cytogenetically related tumors: an immunohistochemical study with diagnostic implications. Am J Surg Pathol. 2012;36:1119–1128. 8. Pulitzer MP, Brannon AR, Berger MF, et al. Cutaneous squamous and neuroendocrine carcinoma: genetically and immunohistochemically different from Merkel cell carcinoma. Mod Pathol. 2015;28: 1023–1032. 9. Yeh I, McCalmont TH. Distinguishing neurofibroma from desmoplastic melanoma: the value of the CD34 fingerprint. J Cutan Pathol. 2011;38: 625–630.
www.amjdermatopathology.com |
Copyright 2016 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
3
Uncommon Tumor, Uncommon Location: A Dermal-Based Spindle Cell/Pleomorphic Lipoma Mark Lincoln, MD and Michael Royer, MD
Abstract: Spindle cell/pleomorphic lipoma is an uncommonly encountered benign neoplasm that is usually found in the subcutaneous tissues. Rare cases reported in the literature have an intradermal location. This lesion usually presents as a subcutaneous nodule on the neck, shoulders, or back of middle-aged to elderly males. Although spindle cell and pleomorphic lipoma are currently considered the same entity, they were historically categorized separately. The authors report a case of hyperpigmented papule with an associated subcutaneous nodule on the left cheek of a 56year-old man, review the literature, and discuss several important diagnostic pitfalls of spindle cell/pleomorphic lipoma. Key Words: skin, neoplasm, benign (Am J Dermatopathol 2016;0:1–3)
INTRODUCTION Spindle cell/pleomorphic lipoma is an uncommon benign soft tissue neoplasm that can rarely occur in the dermis. This unusual presentation can create diagnostic difficulty as the neoplasm is easily confused with other spindle cell processes due to its morphology or with a malignant neoplasm due to its lack of circumscription. Previous terminology of spindle cell/pleomorphic lipomas can also be confusing, as it was originally considered 2 separate entities. We report a case, review the literature, and address the diagnostic challenges of this entity.
adipocytic and spindle cells. The lesion is negative for melan-A, which helps exclude a melanocytic lesion. S100 protein immunohistochemical stain is also negative in the spindle and floret cells, though it highlights the adipocytes. The Ki-67 proliferative index is extremely low (less than 1%). The histologic findings are typical of spindle cell/pleomorphic lipoma (Figs. 3,4).
DISCUSSION Spindle cell/pleomorphic lipoma is a rare, benign adipose tumor. Historically, pleomorphic lipoma and spindle cell lipoma were believed to be separate entities. Further studies demonstrated overlap of their clinical, histologic, and cytogenetic findings.1 They are now considered to be variants of the same entity. The tumor classically presents in the subcutaneous tissues of the shoulders, back, and neck of middle-aged to elderly males as a subcutaneous nodule. Most of these lesions occur in subcutaneous tissues, with a purely intradermal lesion being an unusual presentation.2 Intradermal spindle cell/pleomorphic lipoma has a slight female predominance, as opposed to the male predominance seen in subcutaneous lesions.2,3 Furthermore, intradermal spindle cell/pleomorphic lipomas are most often found on the face.1,3 This is a notably different location compared with the subcutaneous lesion. Clinically, intradermal spindle cell/pleomorphic lipomas are most often diagnosed as a lipoma or a cyst.1 Histopathologically, intradermal and
Case Presentation
A 56-year-old man presented with a slightly raised 8 · 8 mm hyperpigmented, smooth papule on the left cheek with an underlying, freely movable soft subcutaneous nodule. The lesion was present for approximately 2 years. The clinical differential diagnosis included a pigmented nevus. Microscopic examination reveals a nonencapsulated, somewhat ill-defined lesion in the reticular dermis that contains both adipocytes and spindle cells (Fig. 1). The lesion contains a number of large, hyperchromatic “floret-type” cells. Lipoblasts are not seen, and neither mitoses nor necrosis is appreciated (Fig. 2). Immunohistochemical staining shows strong positivity of the floret-type cells for CD34 in both the
From the Department of Pathology, Walter Reed National Military Medical Center, Bethesda, MD. The authors declare no conflicts of interest. Reprints: Mark Lincoln, MD, Department of Pathology, Walter Reed National Military Medical Center. 8901 Wisconsin Ave Bethesda, MD 20889 (e-mail: [email protected]). Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
Am J Dermatopathol Volume 0, Number 0, Month 2016
FIGURE 1. (H&E, ·40) A low power view demonstrates a somewhat ill-defined lesion located in the dermis, consisting of adipocytes and spindle cells. www.amjdermatopathology.com |
Copyright 2016 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
1
Lincoln and Royer
Am J Dermatopathol Volume 0, Number 0, Month 2016
FIGURE 2. (H&E, ·400) A high power view of the spindle cell/ pleomorphic lipoma shows that many of the spindle cells demonstrate striking pleomorphism.
FIGURE 4. (H&E, ·40) A low power view demonstrates a somewhat ill-defined lesion located in the dermis, consisting of adipocytes and spindle cells.
subcutaneous spindle cell/pleomorphic lipomas share many similar features. They are characterized by a proliferation of adipocytes permeated by disorganized spindle cells. The predominant cell type is variable. Large hyperchromatic cells, the floret-type cell, may be observed. Lipoblasts have been reported in some cases.3 Importantly, subcutaneous tumors tend to be well circumscribed, whereas intradermal tumors are usually more infiltrative.4,5 Both intradermal and subcutaneous variants of spindle cell/pleomorphic lipomas may have a myxoid background. A “low fat” or “fat free” variant is reported in the literature that retains all the features of spindle cell/pleomorphic lipomas but has inconspicuous or no adipocytes.6 Overall, these lesions generally have a good prognosis, with excision typically being curative. Some authors have estimated the risk of recurrence to be low, around 1%–2%.3
FIGURE 3. (CD34 immunohistochemical stain, ·200) uniformly strong expression of CD34 is seen in the spindle cells, which permeate throughout the surrounding adipocytes.
Intradermal spindle cell/pleomorphic lipoma presents several pitfalls to the dermatopathologist. Their infiltrative nature raises the possibility of a malignant entity, such as a well-differentiated liposarcoma. Additionally, the presence of lipoblasts may also suggest malignancy. The presence of ropey collagen and loss of Rb protein on immunohistochemistry support the diagnosis of spindle cell/pleomorphic lipoma.7 The RB1 gene is located on chromosome 13q. Deletion of chromosome 13q is characteristic of spindle cell/pleomorphic lipoma, along with loss of chromosome 16q.2 Deletion of chromosome 13q is seen in several other tumors, including mammary-type myofibroblastoma and cellular angiofibroma; loss of nuclear expression for the Rb protein by immunohistochemical stain is an excellent marker for all of these entities.7 Rb protein is also useful in other diagnostic scenarios. For example, cutaneous neuroendocrine carcinoma usually has positive expression, whereas combined squamous-cell carcinoma and neuroendocrine carcinoma have absent Rb expression.8 The rarity of intradermal spindle cell/pleomorphic lipoma makes this entity easy to overlook when considering the histologic differential diagnosis. Prominent myxoid stroma in a spindle cell proliferation may raise the possibility of schwannoma or neurofibroma. The spindle cells in spindle cell/pleomorphic lipoma tend to be stubby, as opposed to the wavy and pointed fibers seen in schwannoma and neurofibroma. Additionally, S-100 protein immunohistochemistry is positive in these 2 entities; whereas it highlights the adipocytes of spindle cell/pleomorphic lipoma; it is negative in spindle cell and floret cells.2,4 Superficial angiomyxoma and myxofibrosarcoma also contain spindle cells in a myxoid stroma and could be considered in the differential diagnosis. Thin-walled, curved blood vessels and neutrophilic infiltrate are characteristic of superficial angiomyxoma and not intradermal spindle cell/pleomorphic lipoma. Myxofibrosarcomas often have thick-walled, curved vessels with adherent tumor cells and tumor cells that resemble myofibroblasts. Intradermal spindle cell/pleomorphic lipomas lack thick-walled
2
Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
| www.amjdermatopathology.com
Copyright 2016 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Am J Dermatopathol Volume 0, Number 0, Month 2016
vessels and usually do not have stellate cells that resemble myofibroblasts.4 CD34 is a helpful marker to rule in spindle cell/ pleomorphic lipoma because the expression is seen in virtually all cases.7 CD34 can be helpful in differentiating spindle cell/pleomorphic lipoma from other entities, but caution is recommended because CD34 can have some degree of positivity in many of the entities in the differential diagnosis. For example, CD34 expression is seen in schwannoma and neurofibroma.2,4 The expression is usually scattered and seen in small spindle cells in these entities, as opposed to the uniformly strong expression seen in spindle cell/pleomorphic lipoma. A “fingerprint” pattern in CD34 is expressed in many neurofibromas, which is useful to differentiate neurofibroma from desmoplastic melanoma, both of which would be highlighted with S100 protein.9 Myxoid dermatofibrosarcoma protuberans also has strong CD34 expression and could be confused with spindle cell/pleomorphic lipoma. Intradermal spindle cell/pleomorphic lipoma is a rare, but benign, lesion that can easily be confused for a more aggressive lesion. We report a case of an intradermal spindle cell/pleomorphic lipoma on the cheek of a 56-year-old male and review the differential diagnosis, immunohistochemical staining pattern, and common diagnostic pitfalls.
Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
Dermal-Based Spindle Cell/Pleomorphic Lipoma
REFERENCES 1. Rubin BP, Fletcher CD. The cytogenetics of lipomatous tumors. Histopathology. 1997;30:507–511. 2. Cheah AL, Billings SD, Goldblum JR, et al. Spindle cell/pleomorphic lipomas of the face: an under-recognized diagnosis. Histopathology. 2015;66:430–437. 3. French CA, Mentzel T, Kutzner H, et al. Intradermal spindle Cell/Pleomorphic lipoma—a distinct subset. Am J Surg Pathol. 2000;22:496–502. 4. Hornick JL, Brooks JS. Soft Tissues. In: Mills SE, Greenson JK, Hornick JL, eds. Sternberg’s Diagnostic Surgical Pathology. Philadelphia, PA: Wolters Kluwer Health; 2015:148–227. 5. Reis-Filho JS, Milanezi F, Soares MF, et al. Intradermal spindle cell/ pleomorphic lipoma of the vulva: case report and review of the literature. J Cutan Pathol. 2001;29:59–62. 6. Billings SD, Folpe AL. Diagnostically challenging spindle cell lipomas: a report of 34 “low-fat” and “fat-free” variants. Am J Dermatopathol. 2007;29:437–442. 7. Chen BJ, Mariño-Enríquez A, Fletcher CD, et al. Loss of retinoblastoma protein expression in spindle cell/pleomorphic lipomas and cytogenetically related tumors: an immunohistochemical study with diagnostic implications. Am J Surg Pathol. 2012;36:1119–1128. 8. Pulitzer MP, Brannon AR, Berger MF, et al. Cutaneous squamous and neuroendocrine carcinoma: genetically and immunohistochemically different from Merkel cell carcinoma. Mod Pathol. 2015;28: 1023–1032. 9. Yeh I, McCalmont TH. Distinguishing neurofibroma from desmoplastic melanoma: the value of the CD34 fingerprint. J Cutan Pathol. 2011;38: 625–630.
www.amjdermatopathology.com |
Copyright 2016 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
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